Add SerialServo lib to the list

[leezisheng]

Add SerialServo lib to the list
https://github.com/leezisheng/SerialServo

[github-actions]

Arduino Lint has suggestions for possible improvements to https://github.com/leezisheng/SerialServo:

Linting library in SerialServo
INFO: No header file found matching library name (SerialServo.h). Best practices are for primary header filename to     
      match library name.                                                                                               
      See: https://arduino.github.io/arduino-cli/latest/library-specification/#libraryproperties-file-format            
      (Rule LS008)                                                                                                      
WARNING: Invalid category field value Motor Control in library.properties                                      
         See: https://arduino.github.io/arduino-cli/latest/library-specification/#libraryproperties-file-format
         (Rule LP038)                                                                                          
WARNING: library.properties includes field item(s) Arduino.h, HardwareSerial.h, assert.h not found in library. 
         See: https://arduino.github.io/arduino-cli/latest/library-specification/#libraryproperties-file-format
         (Rule LP052)                                                                                          
WARNING: No license file found.                                                                                                                 
         See:                                                                                                                                   
         https://docs.github.com/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/licensing-a-repository
         (Rule LD002)                                                                                                                           

Linter results for project: 0 ERRORS, 3 WARNINGS

-------------------

Linting sketch in SerialServo/examples/SerialServoGetData

Linter results for project: no errors or warnings

-------------------

Linting sketch in SerialServo/examples/SerialServoRotation

Linter results for project: no errors or warnings

-------------------

Linter results for projects: 0 ERRORS, 3 WARNINGS

[github-actions]

Your submission has now been accepted! Thanks for your contribution to the Arduino Library Manager index.

The library(s) will be available for installation via Library Manager within a day's time.

You can check the logs from the Library Manager indexer for your library(s) here:
http://downloads.arduino.cc/libraries/logs/github.com/leezisheng/SerialServo/